Process of supporting and cooling shaped hot metal



United States tent No Drawing. Filed Dec. 14, 1960, Ser. No. 75,675 12Claims. (Cl. 1484) This invention relates to a process for supportingshaped hot metal during its cooling'period. More specifically, thisinvention relates to the supporting of hot metal, such as aluminum,magnesium and alloys thereof, after it has been formed, such as byextrusion.

In the extrusion of metals, such as aluminum, into rods or other desiredshapes, it is conventional to heat the metal to a high temperature inorder that it might be conveniently extruded or formed into the desiredshape and size. After the forming step the article must be cooled forsubsequent handling.

Graphite supports such as canisters and run-ou tables have in the pastbeen employed to assist in the cooling operation. These tables may be inthe form of a series of rectangular blocks of equal thickness andtypically are laid lengthwise for a distance sufiicient to bring aboutsubstantial cooling of the formed metal by the time it reaches the endof the run-out table. The top surface of these blocks may be grooved inorder to form a pathway for the metal. Graphite was chosen because ofits ability to withstand high temperatures and at the same time absorband dissipate heat readily. Another reason for its selection was itsrelative softness thereby assuring that it would not scratch the surfaceof the hot and frequently soft metal body sliding over or through it andbeing cooled.

However the employment of graphite for this purpose has one seriousdisadvantage and that is that the graphite marks or blackens the surfaceof the hot metal which contacts and slides along the graphite table orthrough canisters. This marking or blackening has brought seriousobjections from the metal purchasers. It has therefore frequently beennecessary for the metal manufacturer to-remove the objectionable markingfrom the metal. This has required a post-cooling cleaning step or otherpost-cooling processing and costly labor expenses in removing thesemarks from the aluminum.

This invention has as one of its objects the cooling and supporting ofhot metal shapes by graphite and at the same time the substantialelimination of the aforesaid objectionable marking considered inherentwhen employing graphite for this purpose.

The invention has as an additional object the achievement of theforegoing in a convenient, economical and efilcient manner.

It is a finding of this invention that the foregoing objectives may beobtained by subjecting graphite bodies such as previously employed forthese purposes to a post-forming treatment. The graphite bodies whichare subjected to this post-forming treatment will be of any desiredshape, will be porous in nature and will typically have an apparentdensity between about 1.52 and about 1.60. The post-forming treatmentconsists in filling a substantial percentage of the pores of thegraphite bodies with a material found capable of substantiallyeliminating the marking of the hot metal by the graphite. Many materialshave been found to be suitable for this purpose and operative in thepresent invention. They may all be considered as waxy substances and arediscussed in more detail hereinafter.

The waxy substance employed to occupy or fill the pores in thepro-formed graphite bodies may be processed "ice into the pores inseveral different ways such as by soaking the graphite body in thematerial for a sufficient length of time to obtain the desired pickup,impregnating the graphite body by using a normal vacuum-pressure cyclein an autoclave, or by impregnating in an autoclave by pressure alone.The impregnating material may be heated to liquefy it, if necessary,prior to these procedures. It may also be dissolved in a volatilesolvent prior to same or it may sometimes be expedient to employ it asan aqueous emulson. With any of these techniques, the desired pick-up ispreferably from 6 to 12% by weight of solvent-free impregnant based onthe weight of the graphite body with from about 3% to about 25% beingoperative.

Without in any way being bound by theoretical considerations it isbelieved that what occurs as the hot metal slides over the thus treatedgraphite is that the impregnating material continuously migrates bycapillary action toward the surface of the graphite body which iscontacted by the hot metal and thus forms a very thin film at thissurface which prevents or minimizes actual contact between the metal andthe graphite. The graphite body still therefore functions to dissipiatethe heat as desired but does not cause the objectionable marking of thehot metal as has previously been the case. The metal bodies being cooledare frequently at temperatures between 300 and 400 C. and generallybelow 500 C. The materials employed to occupy the pores of the graphitewill typically be solid and have a melting point above 40 C. andpreferably between about 60 C. and about C. The temperature of the hotmetal therefore is high enough to cause melting of the impregnatingmaterial at and near the surface of the graphite body which is contactedby the metal. When the impregnating material at or near the surface ofthe graphite body is raised toward the high temperatures of the metalsbeing cooled, it either vaporizes away from the graphite body or meltsaway from the contacting surface. In either event it is replaced by whatis believed to be capillary action, by some more of the impregnatingmaterial from the pores of the graphite body thereby constantly pIOviding a thin film or barrier between the hot metal and graphite body.

Employing the impregnating materials in accordance with the teachings ofthis invention not only serves to reduce or eliminate the marking of thehot metal by the graphite, but also assists in reducing the friction between the graphite and the hot metal sliding over same. In other wordsit augments the lubricating action of the graphite. This is important inconnection with cases where the metal bodies being cooled are malleableto a degree approaching limpness and where anything that obstructs orinterferes with its smooth and even progress is apt to cause theextruded or formed work to be deformed. It is also important in the caseof heavy extrusions, where a minimum amount of friction is desired.

The pre-formed porous graphite bodies which are subsequently impregnatedmay be made from artificial graphite or electrographite or may be formedfrom a mixture of ordinary coke or carbon particles and pitch and bakedand graphitized in a conventional manner. In any case the bodiesemployed will be those which are porous and which have been pre-formedprior to the addition of the impregnating material. Mantells volume onIndustrial Carbon, 2nd Edition, 1946, pages 268-270, and US. Patent2,862,748 to Bailey et al., particularly column 3, lines 18-35, giveadditional details as to the making of such bodies and their typicalcharacteristics.

The waxy substances employed to impregnate the pores of the graphiteshould be non-halogenated, should not flash into flame when raised to ortoward the temperatures or of the metal bodies being cooled, and shouldnot give oif any obnoxious or harmful fumes when heated.

The waxy substances may be natural Waxes among which are: mineral waxessuch as paraffin wax, petrolatum wax, ozokerite, ceresin, Utah wax andmontan wax; vegetable Waxes such as carnauba wax, flower wax, first wax,medium wax, sandy Wax, fat wax, candelilla wax, Japan wax, Ucuhuba wax,Bayberry wax, Ouricury wax, cocoa butter, fiber Wax, fir-bark wax,cotton wax, flax wax, sugar-cane wax and rice-oil wax; animal waxes suchaslspermaceti; and insect waxes such as beeswax.

The waxy substances employed may also be manufactured andsynthetic'waxes among which are: fatty alcohols such as cetyl alcohol,lanette wax, and stearyl alcohol; fatty acids such as stearic acid,palmitic acid and myristic acid; polyhydric alcohol-fatty acid esterssuch as glyceryl stearates, glycol fatty-acid esters and sorbitolstearates; and hydrogenated oils such as opalwax. Metal salts such asalkali and alkaline earth salts of the fatty acids may also be employed.The employment of mixtures of these materials is also contemplated.Several other suitable waxy materials may be found in BennettsCommercial Waxes, 2nd Edition, 1956, published by Chemical PublishingCo., Inc., 212 Fifth Avenue, New York, N.Y.

Although this invention has been illustrated by'citing specific detailsembraced within the scope of the invention, it is to be understood thatvarious modifications within the invention are possible, some of whichhave been referred to above. I therefore do not Wish to be limitedexcept as defined by the appended claims.

I claim:

1. A process of cooling and supporting solid, heated metal whichcomprises sliding said solid, heated metal in contact with preformed,porous graphite containing a material selected from the group consistingof waxes and metal salts of fatty acids in the pores thereof until asubstantial amount of the heat of the metal has been dissipated by thegraphite.

2. A process of cooling and supporting solid, heated metal whichcomprises sliding said solid, heated metal L1. in contact withpreformed, porous graphite containing a Wax in the pores thereof until asubstantial amount of the heat of the metal .has'been dissipated by thegraphite.

3. The process of claim 1 wherein the hot metal is aluminum.

4. The process of claim 1 wherein the graphite contains from about 3% toabout 25% by Weight of said selected material in the pores thereof.

5. The process of claim 2 wherein the Wax is selected from the groupconsisting of mineral waxes, vegetable waxes, animal waxes, insect waxesand synthetic Waxes.

6. The process of claim 2 wherein the melting point of the wax is atleast 40 C.

7. In the process of cooling solid, heated metal by sliding said solid,heated metal in contact with graphite, the improvement which comprisesemploying preformed, porous graphite containing a material selected fromthe group consisting of Waxes and metal salts of fatty acids in thepores thereof, thereby substantially eliminating any marking of themetal by the graphite.

8. In the process of cooling solid, heated metal by sliding said solid,heated metal in contact with graphite, the improvement which comprisesemploying preformed, porous graphite containing a wax in the poresthereof, thereby substantially eliminating any marking of the metal bythe graphite.

9. The process of claim 7 wherein the hot metal is aluminum.

10. The process of claim 7 wherein the graphite con tains from about 3%to about 25% by weight of said selected material in the pores thereof.

11. The process of claim 8 wherein the wax is selected from the groupconsisting of mineral waxes, vegetable waxes, animal waxes, insect waxesand synthetic waxes.

12. The process of claim 8 wherein the melting point of the wax is atleast 40 C.

Conniif r- Nov. 28, 1911 Parvin Nov. 2, 1943

1. A PROCESS OF COOLING AND SUPPORTING SOLID, HEATED METAL WHICHCOMPRISES SLIDING SAID SOLID, HEATED METAL IN CONTACT WITH PREFORMED,POROUS GRAPHITE CONTAINING A MATERIAL SELECTED FROM THE GROUP CONSISTINGOF WAXES AND METAL SALTS OF FATTY ACIDS IN THE PORES THEREOF UNTIL ASUBSTANTIAL AMOUNT OF THE HEAT OF THE METAL HAS BEEN DISSIPATED BY THEGRAPHITE.